1. Field of the Invention
The invention relates generally to a control apparatus and method for an internal combustion engine, and, more specifically to a control apparatus and method that enables an internal combustion engine installed in a vehicle to start in an appropriate manner.
2. Description of the Related Art
There is an engine control apparatus that is employed in an economy running vehicle equipped with an economy running system or in a hybrid vehicle where the driving source can be switched between the engine and a motor, and that stops the engine when a predetermined engine-stop condition is satisfied and restarts the engine when a predetermined engine-restart condition is satisfied.
For example, Japanese Patent Application Publication No. 2002-339781 (JP-A-2002-339781) describes a control apparatus for a vehicle engine that enables the engine to restart when an engine-restart instruction is issued while the engine is off. The control apparatus includes restart control means for controlling the amount of air taken into the engine while the engine is being restarted in a manner in which the lower the pressure is in an intake pipe of the engine, the greater amount of air is taken into the engine. If an engine-restart instruction is issued when the in-cylinder pressure remains while the engine is off, the control apparatus increases the amount of air is taken into the engine to execute the instruction.
According to the method for restarting the engine described in JP-A-2002-339781, the amount of air taken into the engine while the engine is being restarted may be different each time. This may cause the following inconveniences.
For example, in a hybrid vehicle, when the vehicle is running with low engine efficiency, a motor, instead of the engine, is used as the driving source. On the other hand, when the vehicle is running with high engine efficiency, the engine, instead of the motor, is used as the driving source. When the driving source switches from the motor to the engine, the engine is restarted.
If the amount of air taken into the engine while the engine is being restarted is different each time, the torque output from the engine immediately after the engine starts self-operating may also be different each time. Accordingly, for example, when the torque output from the engine abruptly increases, a driver may sense undesirable vibrations.
Further, if the amount of the air taken into the engine while the engine starts up varies, the air-fuel ratio of the air-fuel mixture to be burned may also vary. This may vary the amount of pollutants in the exhaust gas emitted while the engine starts up. However, JP-A-2002-339781 does not address such inconveniences.